Glossary

The offspring from two plants of different breeds, variety or genetic make-up.

Instantly soluble lime, used to raise or lower ph.

One of several brand names/varieties of clay aggregate medium (also known as LECA for light expanded clay aggregate). It is a lightweight, porous substrate with excellent aeration. Because it does not really wick water effectively, Geolite and other LECA mediums are favorites in ebb-and-flow and drip hydroponic systems.

An instrument for measuring relative humidity in the atmosphere.

A portion of a plant stem between nodes.

This micronutrient acts as a catalyst in the photosynthesis/respiration process, and is essentialp for the formation of sugars and starches. Iron also activates certain other enzymes.

A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-coa derived from carbohydrates, fats and proteins into carbon dioxide and chemical energy.

Leaf malformation due to overwatering, over fertilization, lack of magnesium, insect or fungus damage or negative tropism.

The primary nutrients N-P-K or the secondary nutrients magnesium and calcium.

This micronutrient activates one or more enzymes in fatty acid synthesis; it also activates the enzymes responsible for DNA and RNA production. Closely associated with copper and zinc, manganese also participates directly in the photosynthetic creation of oxygen from water.

The substrate or soilless material which supports the plant and absorbs and releases the nutrient solution in hydroponic horticulture.

Also referred to as trace elements, including S, Fe, Mn, B, Mb, An and Cu.

This micronutrient is essential for nitrogen fixation and nitrate reduction.

The dying of plant tissue, usually the result of serious nutrient deficiency or pest attack.

A hydroponic method in which nutrient is fed into grow tubes or trays in a thin film where the roots draw it up. This “nutrient film” allows the roots to have constant contact with the nutrient and the air layer above at the same time.

A system in which the roots of a plant are consistently or intermittently misted with fine droplets of nutrient solution.

The function of this micronutrient is not well understood, but it is suspected that it might aid carbohydrate transport.

Leaf tips that turn dark from excess fertilizer and salt burn.

This micronutrient is essential for photosynthesis, where it acts as an enzyme activator during the production of oxygen from water.

The condition of a sick plant with yellowing leaves due to inadequate formation of chlorophyll. Chlorosis is caused by a nutrient deficiency, usually iron or nitrogen; nutrient deficiencies are themselves often caused by a ph that is out of the acceptable range.

A plant produced through asexual reproduction including, but not limited to, cuttings, layering and tissue culture.

To soak new Rockwool in an acidic solution to lower the ph from 8.0 to 5.5.

This micronutrient is an internal catalyst and acts as an electron carrier; it is also believed to play a role in nitrogen fixation.

Disease that attacks young seedlings and cuttings, causing stems to rot at the base; overwatering is the main cause of damping-off.